The importance of focusing on entomology in the efforts to eliminate onchocerciasis

Concerted efforts to control the devastating clinical effects of onchocerciasis in Africa began in earnest with the entomologically focused Onchocerciasis Control Programme (OCP) in West Africa 51 y ago. Initially the aim was to reduce the disabling outcomes of the ocular disease that gave the disease its common name ‘river blindness’. The OCP, in general terms, achieved this, at least in West Africa, by reducing vector blackfly breeding through larviciding in eight countries. However, the primary clinical presentation of this infection, skin disfigurement and intense itching, as well as ocular disease, still affected millions of people in endemic areas across Africa, Yemen and in Latin American countries previously involved in the slave trade. The addition of the microfilaricidal agent ivermectin in 1987, through a generous donation by Merck & Co., was a significant boost not only to West African OCP activities but also to those living in all onchocerciasis-endemic areas. In 2000, the World Health Organization (WHO) estimated that some 17 million people were infected, with >250 000 blind and some 500 000 severely visually impaired, and the global goal at that time was to reduce the number of ocular and dermal cases and thus eliminate onchocerciasis as a significant public health problem. In 2010, this international strategy to address onchocerciasis was changed from reducing disease to eliminating transmission, a much higher bar to reach, following the results of studies in Senegal, Mali1 and Nigeria2 that indicated that mass treatment with ivermectin might eliminate onchocerciasis in Africa. This belief contrasts with the collective views of disease experts in 20023 who held that eliminating the transmission of this parasite could be achieved in very limited foci in Latin America but not in Africa unless new tools were developed. Aside from the World Bank–led OCP in West Africa, there have been other concerted, internationally led, collective efforts to coordinate and lead activities aimed at controlling, and latterly eliminating, this parasite and the disease from Africa, Latin America and Yemen. The Carter Centre–led Onchocerciasis Elimination Program for the Americas has been successful in breaking transmission of onchocerciasis in four countries—Mexico, Guatemala, Colombia and Ecuador—and currently focuses on achieving similar successes in Venezuela and Brazil. In the mid-1990s, the WHO’s Regional Office for Africa (AFRO) established the African Programme for Onchocerciasis Control, focusing on community-directed mass treatment with the donated microfilaricidal agent ivermectin. This organization was replaced in 2016 by the also AFRO-based organization the Expanded Special Program to Eliminate NTDs (ESPEN), which has a disease portfolio broader than onchocerciasis alone. Other than research organization-based projects that usually function in countries, such as the US National Institutes of Health–funded projects in Mali and Sudan, ESPEN focused on specific targets, such as improved chemotherapy and understanding the pathogenesis of this disease. Eight years ago, The End Funds’ Reaching the Last Mile Fund (EF-RLMF), supported by His Highness Sheikh Mohamed bin Zayed Al Nahyan of Abu Dhabi, UAE, began eliminating onchocerciasis in six African countries and Yemen. The six African countries in the new RLMF program included three that were involved in the pioneering vector control initiative, the West African OCP (1974–2002)—Senegal, Mali and Niger—and three on the eastern side of Africa—Chad, Sudan and Ethiopia. A key principle in the EF-RMLF’s approach to this challenge was to work closely with each country’s national onchocerciasis program, including working side by side with them wherever requested by the countries. This approach has borne fruit with the recent declaration by one of these countries, Niger, that it has successfully achieved elimination of transmission. Education and understanding are essential to the current and future success of health programs, and nowhere else are they more crucial than in developing countries. As with many of these programs in Africa and elsewhere, continuous training is essential to ensure the quality of health services and activities. This ensures that the various service providers are up to date in their knowledge and procedures and accommodates for the turnover in staff that is an unfortunately common occurrence. National program teams are composed of individuals with personal careers, goals and ambitions and recognising this is a most important contribution to ensuring and maintaining programmatic success. One of the central principles of the EF-RLMF program has been to work with program managers and their national teams as colleagues, especially the younger members. This supplement is an example of EF-RLMF’s commitment to enhancing programs by providing critical career development through information and education. A primary reason for producing this supplement was to act as a framework for training young national entomology researchers. The specific issue-focused manuscripts included in this entomology-oriented supplement have provided these important new scientists with training in the preparation and publication of scientific manuscripts, enhanced their publication record and concurrently created a valuable collection of information that will increase the general understanding of onchocerciasis and its elimination. Providing such support, especially for those who will take national leadership roles in the near future, is a valid demonstration of the often-used, and unfortunately often-misused, term ‘empowering countries’. This supplement is a collection of discussions on essential entomological aspects of programs aimed at breaking transmission of this parasite, all of which are central to the ongoing EF-RLMF program. The issues discussed focus on entomological programmatic factors central to eliminating onchocerciasis transmission, including optimal geographic units for planning and assessment, seasonality and capturing blackflies for analysis. Jamie Tallant (Conceptualization [lead], Funding acquisition [lead]), Charles D. Mackenzie (Writing—original draft [lead], Writing—review & editing [lead]), Daniel Boakye (Conceptualization [lead], Investigation [equal], Project administration [equal]), Anne Heggen (Data curation [equal], Project administration [lead], Writing—original draft [supporting]), Sashi Leff (Funding acquisition [equal], Project administration [equal]), Eve Gatawa (Project administration [equal], Supervision [supporting]), Kelly Zongo (Conceptualization [supporting], Project administration [supporting], Writing—review & editing [supporting]), Martha Mberu (Project administration [equal]) and Pierre Albrieux (Funding acquisition [equal], Project administration [lead]). This supplement was supported by the Reaching the Last Mile Fund (RLMF), a consortium led by His Highness Sheikh Mohamed bin Zayed Al Nahyan, President of the UAE and Ruler of Abu Dhabi, with additional support from the Bill & Melinda Gates Foundation [Grant Number OPP1193778] as a member of the donor consortium of the RLMF at the END Fund. None declared. Not required. The data are available in the article.